Technical Abstract:
As sessile organisms, plants employ multiple mechanisms to cope with seasonal and daily temperature fluctuations associated with their habitats. AtFtsH11 protease gene was identified via map-based cloning as essential for Arabidopsis plant to survive at moderate high temperatures. There are 12 predicted FtsH genes in Arabidopsis genome, with all previously characterized FtsH proteases playing roles in alleviation of light stress. Under high light conditions at 21ºC, ftsh11 mutants were indistinguishable from wild type plants in photosynthesis capacity. However, under temperatures at 30ºC or above, ftsh11 mutants display a host of changes in photosynthetic parameters typical of thermosensitivity and eventually lead to cessation of plant growth and development, and death. Orthologs of AtFtsh11 were identified in pea (PsFtsH11) and rice (OsFtsH11). Overexpression of wild-type AtFtsH11 and PsFtsH11 were able to complement the thermosensitive phenotypes of ftsh11 mutants, suggesting a conserved role of FtsH11 proteases in alleviation of damage caused by high temperatures. Further analysis indicated that FtsH11 play essential roles in the early stages of chloroplast biogenesis and in maintaining thermostability of photosynthetic systems under high temperature stress.